Polarized $J/\psi$ production in semi-inclusive DIS at large $Q^2$: Comparing quark fragmentation and photon-gluon fusion

TL;DR

This paper compares quark fragmentation and photon-gluon fusion mechanisms for polarized J/psi production in semi-inclusive deep inelastic scattering at high Q^2, identifying regimes where each process dominates to facilitate specific measurements.

Contribution

It introduces a comparative analysis of production mechanisms using TMD factorization and NRQCD, highlighting regimes for extracting matrix elements and probing gluon distributions.

Findings

Light quark fragmentation dominates in certain kinematic regimes.

Photon-gluon fusion is dominant in other regimes, enabling gluon TMD PDF extraction.

Identification of regimes for targeted experimental measurements.

Abstract

We compare the relative importance of different mechanisms for polarized $J/\psi$ production in semi-inclusive deep inelastic scattering processes at large $Q^2$. The transverse momentum dependent (TMD) factorization framework and nonrelativistic quantum chromodynamics are used to study the leading contributions from light quark fragmentation to polarized $J/\psi$, and compared to direct production via photon-gluon fusion, which can proceed through color-singlet as well as color-octet mechanisms. We identify kinematic regimes where light quark fragmentation dominates, allowing for the extraction of the $^3S_1^{[8]}$ matrix element, as well as regimes where photon gluon fusion dominates, suggesting that the gluon TMD parton distribution function can be probed.